Some colors humans are exposed to late at night could cause symptoms of clinical depression. That is the conclusion of a study that builds on previous findings that individuals exposed to dim levels of light overnight, such as from a glowing television set, can develop signs of clinical depression.

Investigators, curious as to whether the color of light contributed to depressive symptoms in humans, designed an experiment that exposed hamsters to different colors. They chose hamsters because they are nocturnal, meaning they sleep during the day and are active at night.

One group of hamsters was kept in the dark during their nighttime period. Another group of rodents was exposed to blue light and a third group slept in the presence of white light. A fourth group of hamsters was exposed to glowing red light.

After four weeks, researchers noted how much sugary water the hamsters drank. The more depressed rodents consumed the least amount of water.

Randy Nelson, chair of Ohio State University’s Department of Neuroscience and co-author of the study, said animals that slept in blue and white light appeared to be the most depressed.

“What we saw is these animals didn’t show any sleep disruptions at all but they did have mucked up circadian clock genes and they did show depressive phenotypes whereas if they were in the dim red light, they did not,” Nelson said.

Nelson explained that photosensitive cells in the retina, which don’t have much to do with vision, detect light and transmit signals to the master circadian clock in the brain that controls the natural sleep-wake cycle.

Nelson said there’s a lot of blue in white light, which explains why blue light and white light hamsters seemed more depressed than rodents exposed to red light or darkness.

Nelson had suggestions for so-called "night owls" or people who work the night shift.

“My recommendation is if you are just living a typical mostly active [life] during the day, mostly inactive at night, you want to limit exposure to TVs which are quite bluish in the light they give off and computer screens and things like that," stated Nelson. "You can get filtered glass, you can get filters on your computer screen and filters on your eReaders to put it more in the reddish light.”